Lesson 6: Trigger your flash with an Arduino

Introduction
In the last lesson I showed how to trigger your camera with a flash. In highspeed photography you often want to trigger your flash (see Lesson 3: Freeze the motion with your flash), therefore I show you how to trigger your flash with an arduino.

Idea
With most of my highspeed photos I’ve triggered the flash with an Arduino. As this the base for the following chapters, I’ll show how to trigger a flash. Further I’ll show how you can do multi exposure images, based on this technique. With multi exposure images, you can visualize the motion of a subject.

Camera settings
How to setup the camera for this kind of pictures is described in Lesson 3.

Flash settings
I used one SB28 flashes in ‘repeating flash’ mode. My tests showed that I can trigger the flash every 175ms when using the wireless trigger. I also tried to trigger the flash directly, then I could trigger my flash every 80ms. This mean half of the time -> you’ll have twice as much images of your motion.

Arduino
The arduino doesn’t care whether you’re triggering a flash or a camera, so we can use the stuff from last lesson. The only new thing is a cable to connect the flash with the board. I cut a PC cord and mounted two connectors on each cable. If you shortcut those cables, the flash will trigger.

Highspeed 101 - PC cord for flash triggering

The selfmade cable will now be connected to the flash (or your wireless trigger). As already mentioned, we connect it the very same way we connected our camera in the last lesson.

Highspeed 101 - Breadboard for triggering flash

The arduino was setup to sleep 3 seconds and then trigger the flash 14 times.
To trigger the flash I gave a signal to the gate of the SCR for 20ms and then wait 65ms. I found those value by try and error. The lower these value, the faster motion you can catch, but if those values are to low, the flash will not or not always trigger.

Taking the picture
To take this picture I created a pendulum with a white ball. The ball was accelerated to create a big circle, then the reset button of the Arduino was pressed and finally I started the cam. On the image you can see that the flash triggered 14 times. On the right side, you can see that the images of the ball are overlapped, because there the ball turned in to the direction of the came.

Conclusion
In this lesson I showed how you can trigger a flash with an Arduino and how to create stroboscopic images.